Appearance

The whole system shares one palette: nebelung, a silver-mist Catppuccin variant. It is Catppuccin with the blue pulled out of the greys and the accents calmed down: a fog-grey scheme for people who find most dark themes too loud. Grey is the point. It is named for a cat breed the colour of high fog.

nebelung renders that palette onto 50+ tools (the terminal, the multiplexer, the prompt, git, the file manager, the default editor, the browser), so they all speak the same colours. Three knobs, in the order people reach for them:

They compose, and all three land on the next haus rebuild.

The accent

The greys stay fixed; only the accent hue moves.

haus.theme.accent = "sapphire";

Any of the fourteen Catppuccin accent names works, and the default is mauve:

rosewater · flamingo · pink · mauve · red · maroon · peach · yellow · green · teal · sky · sapphire · blue · lavender

It re-tints the tools that render per-accent variants (lazygit borders, fzf highlights, yazi, glow's markdown headings, the Zen browser, and the generated desktop), while single-file dotfiles keep their built-in theme. That list isn't prose anyone maintains by hand: a build-time check fails if a surface on it starts, or stops, following the accent.

haus.zen.extensions.stylus = { };

Contrast

The default greys are deliberately soft. If text doesn't separate enough (a bright room, a glossy screen, or eyes that want more edge):

haus.theme.contrast = "high";

Same hues, same accents; the neutral ramp is pulled apart in OKLCH so every step gains separation. Contrast is a property of the neutrals only, so a high-contrast machine is the same theme read more easily, not a different one.

haus.accessibility.increaseContrast = true;

Light mode

haus.theme.flavor = "latte";

Light mode is not the dark palette inverted. "Catppuccin with the blue stripped out" says nothing about dark, so the same recipe is applied to Catppuccin Latte instead of Mocha: the same warm-grey ramp and the same calmed accents, read the other way up. Because it is a real re-render, tools take their light-mode branches properly: ANSI black and white swap around, the browser switches its prefers-color-scheme block, delta marks itself light.

The two axes give four palettes. Contrast of body text on the background is measured, not eyeballed, and nebelung's CI holds every one of them above the AAA floor:

haus.theme.systemAppearance = "flavor";  # latte → Light, mocha → Dark

The desktop

The wallpaper is generated on your machine rather than shipped as a picture, and it is what you get without saying anything:

haus.wallpaper.style = "minimal";   # none | minimal | orbits | constellation | flow | bold

minimal is one flat colour out of your palette, the haus mark ⌂ at the centre in the family's six accents, and a very broad bloom in your own accent behind it. There is no photograph to clash with a terminal in front of it, and nothing that stops reading as a background once you have windows open. It is drawn from the palette, accent and gaps you already chose, which is why it can be the default.

style = "none" is a real answer rather than an absence: nothing runs, and whatever wallpaper you have stays exactly where it is. The installer asks.

Preview any of it without rebuilding a Mac:

nix build github:hausfold/haus#wallpaper && open result

Apps you added yourself

Everything above covers the tools haus installs. Apps you put in your Apps you added yourself get the same treatment, as long as the id you keyed the entry under matches a nebelung port:

haus.roster.zed = { key = "x"; name = "Zed"; appId = "dev.zed.Zed"; cask = "zed"; };

On the next rebuild its theme is written where that app looks (~/.config/zed/themes/) in your current flavor, contrast and accent, and re-written whenever you change them. The key is the roster id, not the display name: zed, not zed-editor. haus.theme.ports.enable = false turns the whole pass off.

Dropping a file is enough for apps that read a fixed path. Plenty of others (Xcode, Warp, OBS, JetBrains) have no file interface for choosing a theme, so the file is placed and the one-time pick stays yours. A few (Slack, Raycast) can't be installed by file at all. Rather than leave you to discover that months later, haus doctor says where each one stands:

🌫  Nebelung theme
  ✓ gitui — themed (~/.config/gitui/theme.ron)
  ⓘ Xcode — placed at ~/Library/…/Catppuccin Mocha.xccolortheme — pick it in the app's settings
  ⓘ Slack — not installed — copy the hex string → Slack ▸ Preferences ▸ Themes ▸ paste

A ✓ is live now; a ⓘ tells you the one move left. Ports that would need merging into a config file you own (VS Code's settings.json) are listed but never written: silently half-editing your file is worse than telling you what to do. nebelung's ports table publishes which is which.

Obsidian

Obsidian keeps its theme inside each vault, so haus doesn't guess which folders are yours. List them as home-relative paths:

haus.hearth.obsidianVaults = [
  "Library/Mobile Documents/iCloud~md~obsidian/Documents/notes"
];

Each listed vault gets the generated theme and has it selected; the rest of its appearance settings are preserved. A path without an .obsidian directory is skipped with a warning, so a typo can't create an empty lookalike vault. Obsidian is one of the places light mode doesn't reach yet; it stays dark.

Using nebelung on its own

nebelung is a standalone colour system; you can theme any tool without the rest of haus. Copy a rendered theme out of the flake's output tree, or consume the flake:

inputs.nebelung.url = "github:hausfold/nebelung";
# rendered themes:  ${nebelung.packages.${system}.default}/<tool>/...
# raw palette:      nebelung.palette          # name → "#hex"

glow, lazygit, yazi and the browser render all fourteen accents as separate files; the other tools ship one theme with the default accent baked in. Every hex, and an interactive preview of all four variants, is in the nebelung repo.

Colours are generated at build time from that one source rather than loaded from loose theme files, which is why the palette can never drift out of sync: update nebelung, rebuild, and every tool gets the same new values at once.

Want a different fog? The palette is computed in OKLCH from three knobs (the grey's hue and chroma, and how far the accents are calmed), so hue and saturation can be rewritten while perceptual lightness is preserved. That is a change in the nebelung repo, not in your host file.

Works with

• Displays: haus.appearance.largePrint is one line for bigger type: it moves the interface scale, the contrast, macOS's own contrast lift and displays.main.uiScale together, each as a default you can still pin by hand.
• Apps: anything you add whose id nebelung has a port for is themed too.
• Every other room takes its colours from here rather than declaring its own.

Permissions and side effects

Following macOS's own Light/Dark needs an Automation grant for whatever runs your rebuild (System Settings ▸ Privacy & Security ▸ Automation), as light mode describes. Theme ports write files into apps haus did not install; that's the point of them, and haus.theme.ports.enable = false stops it.

Remove it

The room has no off switch, because a machine with no colours is not a thing anyone wants. The parts do:

haus.theme.ports.enable = false;   # stop writing themes into other apps
haus.wallpaper.style = "none";     # keep the desktop picture you had
haus.appearance.largePrint = false;

Options

Every setting, with types and defaults: Appearance.